High voltage device

ABSTRACT

A high-voltage device includes a substrate, a first well region disposed in the substrate, at least a first isolation, a frame-like gate structure over the first well region and covering a portion of the first isolation, a drain region in the first well region and separated from the frame-like gate structure by the first isolation, and a source region separated from the drain region by the first isolation and the frame-like gate structure. The first well region, the drain region and the source region include a first conductivity type, and the substrate includes a second conductivity type. The first conductivity type and the second conductivity type are complementary to each other.

PRIORITY DATA

This patent claims the benefit of U.S. Provisional Patent ApplicationSer. No. 62/942,049 filed Nov. 29, 2019, the entire disclosure of whichis hereby incorporated by reference.

BACKGROUND

Technological advances in semiconductor integrated circuit (IC)materials, design, processing, and manufacturing have enabled thecontinual reduction in size of IC devices, where each generation hassmaller and more complex circuits than the previous generation.

As semiconductor circuits composed of devices such asmetal-oxide-semiconductor field-effect transistors (MOSFETs) are adaptedfor high voltage applications, such as high-voltage lateral diffusionmetal-oxide-semiconductor (HV LDMOS) devices, problems arise withrespect to decreasing voltage performance as the downscaling continueswith advanced technologies. To prevent punch-through between source anddrain, or to reduce resistance of the source and drain, standard MOSfabrication process flows may be accompanied by multiple implantationsof high concentrations. Substantial substrate leakage and voltagebreakdown often occur with device reliability degradation.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a top view of a high-voltage device according to aspects ofthe present disclosure in one or more embodiments.

FIG. 2 is a cross-sectional view taken along line FIG. 1.

FIG. 3 is a top view of a high-voltage device according to aspects ofthe present disclosure in one or more embodiments.

FIG. 4 is a cross-sectional view taken along line II-II′ of FIG. 3.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat references numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

This description of illustrative embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. In the description ofembodiments disclosed herein, any references to direction or orientationare merely intended for convenience of description and are not intendedin any way to limit the scope of the present disclosure. Relative termssuch as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,”“up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g.,“horizontally,” “downwardly,” “upwardly,” etc.) should be construed torefer to the orientation as then described or as shown in the drawingunder discussion. These relative terms are for convenience ofdescription only and do not require that the apparatus be constructed oroperated in a particular orientation. Terms such as “attached,”“affixed,” “connected” and “interconnected” refer to a relationshipwherein structures are secured or attached to one another eitherdirectly or indirectly through intervening structures, as well as bothmovable or rigid attachments or relationships, unless expresslydescribed otherwise. Moreover, the features and benefits of thedisclosure are illustrated by references to the embodiments.Accordingly, the disclosure expressly should not be limited to suchembodiments illustrating some possible non-limiting combination offeatures that may exist alone or in other combinations of features, thescope of the disclosure being defined by the claims appended hereto.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in therespective testing measurements. Also, as used herein, the terms“substantially,” “approximately” or “about” generally mean within avalue or range that can be contemplated by people having ordinary skillin the art. Alternatively, the terms “substantially,” “approximately” or“about” mean within an acceptable standard error of the mean whenconsidered by one of ordinary skill in the art. People having ordinaryskill in the art can understand that the acceptable standard error mayvary according to different technologies. Other than in theoperating/working examples, or unless otherwise expressly specified, allof the numerical ranges, amounts, values and percentages such as thosefor quantities of materials, durations of times, temperatures, operatingconditions, ratios of amounts, and the likes thereof disclosed hereinshould be understood as modified in all instances by the terms“substantially,” “approximately” or “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thepresent disclosure and attached claims are approximations that can varyas desired. At the very least, each numerical parameter should beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. Ranges can be expressed herein asbeing from one endpoint to another endpoint or between two endpoints.All ranges disclosed herein are inclusive of the endpoints, unlessspecified otherwise.

Typically, it is required that a high-voltage device has low anti-punchcapability between the source/body and the substrate. In somecomparative approaches, an n-type buried doped layer and a p-type dopedregion are formed in a high-voltage device, such that the high-voltagedevice can be fully isolated from the substrate. In other comparativeapproaches, a width of the n-type buried doped layer can be increased tosustain high voltage during an off-state and high-voltage gap betweenthe source/body and the substrate in the large cell array application.However, a large area penalty will be incurred by such increased width.

Further, breakdown voltage (BVD) and on-resistance (Ron) are twoimportant characteristics of a high-voltage device used in a powerswitch circuit. Improving the operation of a power switch circuitincorporating MOSFETs suggests using a MOSFET with a breakdown voltageas high as possible and an on-resistance as low as possible. However, inorder to improve the anti-punch capability, the large area for adoptingthe large n-type buried doped layer causes the high-voltage device tosuffer from increased on-resistance.

The present disclosure therefore provides a high-voltage device having aframe-like gate structure. The frame-like gate structure helps to reducecurrent from the drain region through the drift region. Accordingly,breakdown voltage and anti-punch capability of the high-voltage devicecan be increased. Further, because the frame-like gate helps to improvethe anti-punch capability, a width of the n-type doped layer can bereduced, such that on-resistance can be reduced. In other words, thehigh-voltage device including the frame-like gate structure has anincreased breakdown voltage, an improved anti-punch capability, andreduced on-resistance.

In some embodiments, a high-voltage device 100 is provided. Thehigh-voltage device 100 can be an n-type high-voltage device, but thedisclosure is not limited thereto. In some embodiments, the high-voltagedevice 100 can be referred to as a high-voltage laterally-diffused MOS(HV LDMOS) transistor device, a high-voltage extended-drain MOS HVEDMOS) transistor device, or any other HV device.

Referring to FIGS. 1 and 2, FIG. 1 illustrates a top view of ahigh-voltage device 100, and FIG. 2 is a cross-sectional view takenalong line I-I′ of FIG. 1. In some embodiments, the high-voltage device100 includes a substrate 102 (shown in FIG. 2). The substrate 102 caninclude an elementary semiconductor including silicon or germanium in asingle crystal form, a polycrystalline form, or an amorphous form; acompound semiconductor material including at least one of siliconcarbide, gallium arsenide, gallium phosphide, indium phosphide, indiumarsenide, and indium antimonide; an alloy semiconductor materialincluding at least one of SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP,and GaInAsP; any other suitable material; or a combination thereof. Insome embodiments, the alloy semiconductor substrate may a SiGe alloywith a gradient Ge feature in which the Si and Ge composition changesfrom one ratio at one location to another ratio at another location ofthe gradient SiGe feature. In another embodiment, the SiGe alloy isformed over a silicon substrate. In some embodiments, a SiGe alloy canbe mechanically strained by another material in contact with the SiGealloy. Furthermore, the substrate 102 may be a semiconductor oninsulator, such as silicon on insulator (SOI). In some embodiments, thesubstrate 102 may include a doped epitaxial layer or a buried layer. Insome embodiments, the substrate 102 may have a multilayer structure, orthe substrate 102 may include a multilayer compound semiconductorstructure.

The high-voltage device 100 includes a well region 110 disposed in thesubstrate 102. In some embodiments, the well region 110 includes a firstconductivity type, and the substrate 102 includes a second conductivitytype. The first conductivity type and the second conductivity type arecomplementary to each other. In some embodiments, the first conductivitytype is an n type, and the second conductivity type is a p type. In someembodiments, n-type dopants include arsenic (As), phosphorus (P), othergroup V elements, or any combination thereof. In some embodiments,p-type dopants include boron (B), other group III elements, or anycombination thereof. Although the substrate 102 and the well region 110include dopants of different types, a doping concentration of the wellregion 110 is greater than a doping concentration of the substrate 102.The well region 110 can be referred to as a drift region. In someembodiments, the well region 110 can be referred to as a high-voltagen-type well (HVNW).

In some embodiments, the high voltage device 100 includes an isolation104, such as a frame-like isolation 104 disposed in the well region 110.In some embodiments, the isolation 104 can be a shallow trench isolation(STI), as shown in FIG. 2. In other embodiments, the isolation 104includes a structure of a local oxidization of silicon (LOCOS)structure, or any other suitable isolation structure. As shown in FIGS.1 and 2, a bottom of the well region 110 is in contact with thesubstrate 102, and side edges 110 e of the well region 110 are under theframe-like isolation 104. In some embodiments, the frame-like isolation104 can be said to surround the well region 110. As shown in FIG. 2, theisolation 104 is partially disposed in the well region 110.

In some embodiments, the high-voltage device 100 includes anotherisolation 106, for example, a frame-like isolation 106. As mentionedabove, the isolation 106 can be an STI, a LOCOS structure, or any othersuitable isolation structure. A width of the isolation 104 and a widthof the isolation 106 can be similar or different, depending on differentproduct designs. A depth of the isolation 104 and a depth of theisolation 106 are similar. As shown in FIG. 2, the isolation 106 isdisposed in well region 110, and a bottom surface and side edges of theisolation 106 are in contact with the well region 110.

The high-voltage device 100 further includes a well region 112 disposedin the well region 110. The well region 112 can be a frame-like wellregion 112 disposed between the isolation 104 and the isolation 106, asshown in FIG. 2. In some embodiments, at least a portion of side edgesof the well region 112 is in contact with the well region 110, and aportion of a bottom of the well region 112 is in contact with the wellregion 110. The well region 112 can include the second conductivitytype. In some embodiments, the well region 112 can be referred to as ahigh-voltage p-type well (HVPW). In some embodiments, the well region112 is separated from the substrate 102 by the well region 110.

The high-voltage device 100 further includes a well region 114. The wellregion 114 is partially disposed in the well region 110 and partially inthe well region 112, as shown in FIG. 2. In some embodiments, a bottomsurface of the well region 114 is lower than a bottom surface of thewell region 112, and thus the well region 114 can be referred to as adeep p-type well (DPW). As shown in FIG. 2, the bottom surface of thewell region 114 is in contact with the well region 110. The well region114 can include the second conductivity type. In some embodiments, adoping concentration of the well region 114 is greater than a dopingconcentration of the well region 112.

The high-voltage device 100 includes a frame-like gate structure 120disposed on the substrate 102. As shown in FIGS. 1 and 2, the frame-likegate structure 120 covers a portion of the isolation 106 and a portionof the well region 110. However, the frame-like gate structure 120 isseparated from the isolation 104. Further, the frame-like gate structure120 may be surrounded by the well region 112. In some embodiments, achannel is formed in the well region 110 directly under the frame-likegate structure 120. The frame-like gate structure 120 includes a firstaxis Ax1 and a second axis Ax2, wherein the first axis Ax1 isperpendicular to the second axis Ax2. In some embodiments, a length ofthe first axis Ax1 and a length of the second axis Ax2 are similar, suchthat the frame-like gate structure 120 has a point symmetryconfiguration and a line symmetry configuration, but the disclosure isnot limited thereto.

In some embodiments, the frame-like gate structure 120 includes a gateconductive layer 122 and a gate dielectric layer 124 between the gateconductive layer 122 and the substrate 102. The gate conductive layer122 can include polysilicon, silicon-germanium, and at least onemetallic material including elements and compounds such as Mo, Cu, W,Ti, Ta, TiN, TaN, NiSi, CoSi, or other suitable conductive materialsknown in the art. In some embodiments, the gate conductive layer 122includes a work function metal layer that provides a metal gate with ann-type-metal work function or p-type-metal work function. Thep-type-metal work function materials include materials such asruthenium, palladium, platinum, cobalt, nickel, conductive metal oxide,or other suitable materials. The n-type-metal work function materialsinclude materials such as hafnium, zirconium, titanium, tantalum,aluminum, metal carbides (e.g., hafnium carbide, zirconium carbide,titanium carbide, and aluminum carbide), aluminides, or other suitablematerials.

The gate dielectric layer 124 can have a single layer or a multi-layerstructure. In some embodiments, the gate dielectric layer 124 is amulti-layer structure that includes an interfacial layer and a high-kdielectric layer. The interfacial layer can include dielectric materialsuch as silicon oxide, silicon nitride, silicon oxynitride, otherdielectric material, or a combinations thereof. The high-k dielectriclayer can include high-k dielectric material such as HfO₂, HfSiO,HfSiON, HfTaO, HfTiO, HfZrO, other suitable high-k dielectric materials,or a combinations thereof. In some embodiments, the high-k dielectricmaterial can further be selected from metal oxides, metal nitrides,metal silicates, transition metal-oxides, transition metal-nitrides,transition-metal silicates, metal oxynitrides, metal aluminates, andcombinations thereof.

In some embodiments, the frame-like gate structure 120 may includespacers 126 i and 126 o disposed over sidewalls. In some embodiments,the frame-like gate structure 120 includes an inner spacer 126 idisposed over an inner sidewall of the frame-like gate structure 120,and an outer spacer 126 o disposed over an outer sidewall of theframe-like gate structure 120. As shown in FIG. 2, the inner spacer 126i may be disposed over the isolation 106, while the outer spacer 126 ois disposed over the substrate 120. It should be noted that the innerspacer 126 i and the outer spacer 126 o are omitted from FIG. 1 forclarity; however, those skilled in the art should easily realizelocations of the inner and outer spacers 126 i and 126 o according toFIG. 2.

Still referring to FIGS. 1 and 2, the high-voltage device 100 includes adrain region 130D and a doped region 132 disposed in the well region110. Further, the drain region 130D and the doped region 132 areenclosed by the frame-like isolation 106. In other words, the drainregion 130D and the doped region 132 are disposed in a central regionwithin the frame-like isolation 106 and the frame-like gate structure120, as shown in FIG. 1. The drain region 130D and the doped region 132are separated from the frame-like gate structure 120 by the frame-likeisolation 106, as shown in FIG. 2. The doped region 132 is disposedunder the drain region 130D. Further, the doped region 132 is separatedfrom the substrate 102 by the well region 110. In some embodiments, sideedges of the drain region 130D are in contact with the isolation 106,and a bottom surface of the drain region 130D is in contact with thedoped region 132. The drain region 130D and the doped region 132 includethe first conductivity type. A doping concentration of the drain region130D is greater than a doping concentration of the doped region 132.

The high-voltage device 100 includes a source region 1305 in thesubstrate 102 and adjacent to the frame-like gate structure 120 on aside opposite to the drain region 130D. The source region 130S istherefore separated from the drain region 130D by the frame-like gatestructure 120 and the frame-like isolation 106. The source region 130Sincludes the first conductivity type, and a doping concentration of thesource region 130S is similar to the doping concentration of the drainregion 130D. In some embodiments, the source region 130S disposedbetween the frame-like gate structure 120 and the isolation 104 has aframe-like configuration surrounding the frame-like gate structure 120,as shown in FIG. 1.

In some embodiments, the high-voltage device 100 further includes adoped region 140. The doped region 140 is adjacent to the source region130S. The doped region 140 includes the second conductivity type. Insome embodiments, the doped region 140 has a frame-like configurationsurrounding the frame-like source region 130S, as shown in FIG. 1. Insome embodiments, the doped region 140 serves as a body pickup region. Aperson skilled in the art will recognize that there may be manyalternatives, modifications and variations. For example, depending ondifferent applications and design needs, the body pickup region 140 andthe source region 130S may share a contact plug.

Additionally, a silicide structure (not shown) can be formed on thedrain region 130D, the source region 130S and the doped region 140. Thesilicide structure may include materials such as nickel silicide (NiSi),nickel-platinum silicide (NiPtSi), nickel-platinum-germanium silicide(NiPtGeSi), nickel-germanium silicide (NiGeSi), ytterbium silicide(YbSi), platinum silicide (PtSi), iridum silicide (IrSi), erbiumsilicide (ErSi), cobalt silicide (CoSi), other suitable materials, or acombination thereof.

The high-voltage device 100 further includes a doped region 142 disposedin the well region 110. In some embodiments, the doped region 142 alsohas a frame-like configuration surrounding the frame-like gate structure120. However, because the doped region 142 is partially covered by theframe-like gate structure 120, partially covered by the source region1305 and the doped region 140, and partially covered by the isolation104, the doped region 142 may not be observed from the top view. Thedoped region 142 includes the second conductivity type. Further, adoping concentration of the doped region 142 is less than a dopingconcentration of the doped region 140. In some embodiments, the dopingconcentration of the doped region 142 may between approximately2.5E+15/cm³ and approximately 3.5E+18/cm³, but the disclosure is notlimited thereto. In some embodiments, the doped region 142 can bereferred to as a high-voltage p-type body (HVPB). In some embodiments, aside edge of the doped region 142 can be in contact with the well region110.

The high-voltage device 100 further includes another doped region 144under the doped region 142, and separated from the well region 110 bythe well region 112. In some embodiments, the doped region 144 also hasa frame-like configuration surrounding the frame-like gate structure120. The doped region 144 includes the second conductivity type.Further, the doping concentration of the doped region 142 is greaterthan a doping concentration of the doped region 144. In someembodiments, a top surface of the doped region 144 is in contact withthe doped region 142, and side edges and a bottom surface of the dopedregion 144 are in contact with the well region 112.

In some embodiments, the high-voltage device 100 includes anotherisolation 108, such as a frame-like isolation 108 surrounding theisolation 104, the well regions 110, 112 and 114, the doped regions 140,142 and 144, the source region 1305, the frame-like gate structure 120and the drain region 130D.

In some embodiments, a doped region 150 is formed between the isolation104 and the isolation 108. Further, a doped region 152 and a well region154 may be formed under the doped region 150. The doped region 150, thedoped region 152 and the well region 154 include the second conductivitytype. A doping concentration of the doped region 150 is greater than adoping concentration of the doped region 152, and the dopingconcentration of the doped region 152 is greater than a dopingconcentration of the well region 154. In some embodiments, the dopedregion 152 is disposed under the doped region 150 such that a bottomsurface of the doped region 150 is in contact with the doped region 152.The well region 154 is formed under the doped region 152, such that abottom surface and side edges of the doped region 152 are in contactwith the well region 154. In some embodiments, the well region 154 is incontact with the well region 110.

In some embodiments, the doped region 150 may serve as a guard ring forthe high-voltage device 100. The doped region 150 allows an electricalbias to be applied to the substrate 102 through the doped region 152 andthe well region 154. It should be understood that the formation of thedoped region 150 is optional.

According to some embodiments of the high-voltage device 100, an edge112 e of the well region 112 is in contact with the well region 110.Further, a distance d can be defined between the edge 112 e of the wellregion 112 and the edge 110 e of the well region 110, as shown in FIG.2. In some embodiments, the distance d can be between approximately 2 μmand approximately 3 μm. In some comparative approaches, when thedistance d between the edge 112 e and the edge 110 e is less than 2 μm,current may punch through the well region 110, and thus such device mayfail. In alternative comparative approaches, when the distance d betweenthe edge 112 e and the edge 110 e is greater than 3 μm, such device mayneed more area to accommodate the well region and thus cannot be shrunk.In contrast to the comparative approaches, an anti-punch capability ofthe high-voltage device 100 can be improved by greater thanapproximately 300%.

It should be noted that a drain-to-source breakdown voltage is thevoltage below which the respective device (such as the high-voltagedevice 100) may operate. When a voltage greater than the breakdownvoltage is applied, catastrophic and irreversible damage is caused tothe device, rendering the device commercially useless and requiring thedevice to be replaced. Accordingly, increasing the breakdown voltage ishighly desirable. In the high-voltage device 100, the gate structure 120has the frame-like configuration. Accordingly, the well region 110 underthe frame-like gate structure 120 can be fully depleted when thehigh-voltage device 100 is in an off state. In other words, a frame-likefully depleted region A may be formed when the high voltage device 100is in off state. The frame-like fully-depleted region A helps toincrease the breakdown voltage. In some embodiments, the breakdownvoltage of the high-voltage device 100 can be improved by greater thanapproximately 27%. Because a channel width of the frame-like gatestructure 120 is increased by the point symmetry configuration and theline symmetry configuration, an on-resistance of the high-voltage device100 can be reduced.

Additionally, the high-voltage device 100 has a point symmetryconfiguration and a line symmetry configuration, but the disclosure isnot limited thereto.

Referring to FIGS. 3 and 4, FIG. 3 illustrates a top view of a highvoltage device 200, and FIG. 4 is a cross-sectional view taken alongline II-II′ of FIG. 3. It should be noted that details, such asmaterials, of same elements shown in FIGS. 1 and 3 and FIGS. 2 and 4 areomitted for brevity. In some embodiments, the high-voltage device 200includes a substrate 202 (shown in FIG. 4). The high-voltage device 200includes well regions 210-1 and 210-2. In some embodiments, the \veilregions 210-1 and 210-2 include a first conductivity type, and thesubstrate 202 includes a second conductivity type. The firstconductivity type and the second conductivity type are complementary toeach other. In some embodiments, the first conductivity type is an ntype, and the second conductivity type is a p type. Although thesubstrate 202 and the well regions 210-1, 210-2 include dopants ofdifferent types, a doping concentration of the well regions 210-1 and210-2 is greater than a doping concentration of the substrate 202.Further, the doping concentration of the well region 210-1 and thedoping concentration of the well region 210-2 are the same. The wellregions 210-1 and 210-2 can be referred to as a drift region. In someembodiments, the well regions 210-1 and 210-2 can be referred to as ahigh-voltage n-type well (HVNW).

In some embodiments, the high-voltage device 200 includes a frame-likeisolation 204-1 and a frame-like isolation 204-2 disposed in thesubstrate 202. As shown in FIGS. 3 and 4, the frame-like isolation 204-1and the frame-like isolation 204-2 are separated from each other. Insome embodiments, the frame-like isolations 204-1 and 204-2 can be STI,as shown in FIG. 4. In other embodiments, the frame-like isolation 204-1and the frame-like isolation 204-2 include a structure of a LOCOSstructure, or any other suitable isolation structure. A width and adepth of the frame-like isolation 204-1 are similar to a width and adepth of the frame-like isolation 204-2. As shown in FIGS. 3 and 4,bottoms of the well regions 210-1 and 210-2 are in contact with thesubstrate 202. Side edges 210 e-1 of the well region 210-1 are under theframe-like isolation 204-1, and side edges 210 e-2 of the well region210-2 are under the frame-like isolation 204-2. In some embodiments, theframe-like isolation 204-1 can be said to surround the well region210-1, and the frame-like isolation 204-2 can be said to surround thewell region 210-2. As shown in FIG. 4, the frame-like isolation 204-1 ispartially disposed in the well region 210-1, and the frame-likeisolation 204-2 is partially disposed in the well region 210-2.

In some embodiments, the high-voltage device 200 includes a frame-likeisolation 206-1 and a frame-like isolation 206-2 separated from eachother. As mentioned above, the frame-like isolations 206-1 and 206-2 canbe an STI a LOCOS structure, or any other suitable isolation structure.A width of the frame-like isolations 204-1, 204-2 and a width of theframe-like isolations 206-1, 206-2 can be similar or different,depending on different product designs. A depth of the frame-likeisolations 204-1, 204-2 and a depth of the frame-like isolations 206-1,206-2 are similar. The frame-like isolation 206-1 is disposed in thewell region 210-1, and the frame-like isolation 206-2 is disposed in thewell region 210-2. As shown in FIG. 4, a bottom surface and side edgesof the frame-like isolation 206-1 are in contact with the well region210-1, and a bottom surface and side edges of the frame-like isolation206-2 are in contact with the well region 210-2.

The high-voltage device 200 further includes a frame-like well region212-1 disposed in the well region 210-1, and a frame-like well region212-2 in the well region 210-2. The frame-like well region 212-1 isdisposed between the frame-like isolation 204-1 and the frame-likeisolation 206-1, while the frame-like well region 212-2 is disposedbetween the frame-like isolation 204-2 and the frame-like isolation206-2, as shown in FIG. 4. In some embodiments, at least a portion ofside edges of the frame-like well region 212-1 is in contact with thewell region 210-1, and a portion of a bottom of the frame-like wellregion 212-1 is in contact with the well region 210-1. Similarly, atleast a portion of side edges of the frame-like well region 212-2 is incontact with the well region 210-2, and a portion of a bottom of theframe-like well region 212-2 is in contact with the well region 210-2.The frame-like well regions 212-1 and 212-2 can include the secondconductivity type. A doping concentration of the frame-like well region212-1 and a doping concentration of the frame-like well region 212-2 arethe same. In some embodiments, the frame-like well regions 212-1 and212-2 can be referred to as high-voltage p-type wells (HVPW). Further,the frame-like well regions 212-1 and 212-2 are separated from eachother.

The high-voltage device 200 further includes frame-like well regions214-1 and 214-2 separated from each other. The frame-like well region214-1 is partially disposed in the well region 210-1 and partially inthe frame-like well region 212-1, and the frame-like well region 214-2is partially disposed in the well region 210-2 and partially in theframe-like well region 212-2, as shown in FIG. 4, in some embodiments, abottom surface of the frame-like well region 214-1 is lower than abottom surface of the frame-like well region 212-1; therefore, a bottomsurface of the frame-like well region 214-1 is in contact with the wellregion 210-1. Similarly, a bottom surface of the frame-like well region214-2 is in contact with the well region 210-2. Thus, the frame-likewell regions 214-1 and 214-2 can be referred to as deep p-type wells(DPW). The frame-like well regions 214-1 and 214-2 can include thesecond conductivity type. In some embodiments, a doping concentration ofthe frame-like well regions 214-1 and 214-2 is greater than a dopingconcentration of the frame-like well regions 212-1 and 212-2. Further,the doping concentration of the frame-like well region 214-1 and thedoping concentration of the frame-like well region 214-2 are the same.

The high-voltage device 200 includes frame-like gate structures 220-1and 220-2 separated from each other. As shown in FIGS. 3 and 4, theframe-like gate structure 220-1 covers a portion of the frame-likeisolation 206-1 and a portion of the well region 210-1, and theframe-like gate structure 220-2 covers a portion of the frame-likeisolation 206-2 and a portion of the well region 210-2. The frame-likegate structure 220-1 is separated from the frame-like isolation 204-1,and the frame-like gate structure 220-2 is separated from the frame-likeisolation 204-2. Further, the frame-like gate structure 220-1 may besurrounded by the frame-like well region 212-1, and the frame-like gatestructure 220-2 may be surrounded by the frame-like well region 212-2.The frame-like gate structures 220-1 and 220-2 respectively include afirst axis Ax1 and a second axis Ax2, and the first axis Ax1 isperpendicular to the second axis Ax2. In some embodiments, a length ofthe first axis Ax1 is greater than a length of the second axis Ax2, asshown in FIG. 3.

In some embodiments, the frame-like gate structures 220-1 and 220-2respectively include a gate conductive layer 222 and a gate dielectriclayer 224 between the gate conductive layer 222 and the substrate 202.The gate dielectric layer 224 can have a single layer or a multi-layerstructure. In some embodiments, the gate dielectric layer 224 is amulti-layer structure that includes an interfacial layer and a high-kdielectric layer. In some embodiments, each of the frame-like gatestructures 220-1 and 220-2 may include spacers 226 i and 226 o disposedover sidewalls. In some embodiments, each of the frame-like gatestructures 220-1 and 220-2 includes an inner spacer 226 i disposed overan inner sidewall and an outer spacer 226 o disposed over an outersidewall. As shown in FIG. 4, the inner spacer 226 i may be disposedover the frame-like isolation 206-1 or 206-2, while the outer spacer 226o is disposed over the substrate 202. Additionally, it should be notedthat the inner spacer 226 i and the outer spacer 226 o are omitted fromFIG. 3 for clarity, however, those skilled in the art should easilyrealize locations of the inner and outer spacers 226 i and 226 oaccording to FIG. 4.

Still referring to FIGS. 3 and 4, the high-voltage device 200 includes adrain region 230D-1 and a doped region 232-1 disposed in the well region210-1, and a drain region 230D-2 and a doped region 232-2 disposed inthe well region 210-2. Further, the drain region 230D-1 and the dopedregion 232-1 are enclosed by the frame-like isolation 206-1, and thedrain region 230D-2 and the doped region 232-2 are enclosed by theframe-like isolation 206-2. In other words, the drain region 230D-1 andthe doped region 232-1 are disposed in a central region within theframe-like isolation 206-1 and the frame-like gate structure 220-1,while the drain region 230D-2 and the doped region 232-2 are disposed ina central region within the frame-like isolation 206-2 and theframe-like gate structure 220-2, as shown in FIG. 3. The drain region230D-1 and the doped region 232-1 are separated from the frame-like gatestructure 220-1 by the frame-like isolation 206-1, and the drain region230D-2 and the doped region 232-2 are separated from the frame-like gatestructure 220-2 by the frame-like isolation 206-2, as shown in FIG. 4.The doped regions 232-1 and 232-2 are disposed under the drain regions230D-1 and 230D-2. Further, the doped region 232-1 is separated from thesubstrate 202 by the well region 210-1, and the doped region 232-2 isseparated from the substrate 202 by the well region 210-2. In someembodiments, side edges of the drain region 230D-1 are in contact withthe frame-like isolation 206-1, and a bottom surface of the drain region230D-1 is in contact with the doped region 232-1. Similarly, side edgesof the drain region 230D-2 are in contact with the frame-like isolation206-2, and a bottom surface of the drain region 230D-2 is in contactwith the doped region 232-2. The drain regions 230D-1, 230D-2 and thedoped regions 232-1, 232-2 include the first conductivity type. A dopingconcentration of the drain regions 230D-1, 230D-2 is greater than adoping concentration of the doped regions 232-1, 232-2.

The high-voltage device 200 includes a frame-like source region 230S-1in the substrate 202 and adjacent to the frame-like gate structure 220-1on a side opposite to the drain region 230D-1, and a frame-like sourceregion 230S-2 in the substrate 202 and adjacent to the frame-like gatestructure 220-2 on a side opposite to the drain region 230D-2. Theframe-like source region 230S-1 is therefore separated from the drainregion 230D-1 by the frame-like gate structure 220-1 and the frame-likeisolation 206-1. Similarly, the frame-like source region 230S-2 istherefore separated from the drain region 230D-2 by the frame-like gatestructure 220-2 and the frame-like isolation 206-2. The frame-likesource regions 230S-1 and 230S-2 include the first conductivity type,and a doping concentration of the frame-like source regions 230S-1 and230S-2 is similar to the doping concentration of the drain regions230D-1 and 230D-2. Further, the frame-like source region 230S-1 isdisposed between the frame-like gate structure 220-1 and the frame-likeisolation 204-1 and surrounds the frame-like gate structure 220-1, whilethe frame-like source region 230S-2 is disposed between the frame-likegate structure 220-2 and the frame-like isolation 204-2 and surroundsthe frame-like gate structure 220-2.

In some embodiments, the high-voltage device 200 further includes aframe-like doped region 240-1 adjacent to the frame-like source region230S-1, and a frame-like doped region 240-2 adjacent to the frame-likesource region 230S-2. The frame-like doped regions 240-1 and 240-2include the second conductivity type. In some embodiments, theframe-like doped regions 240-1 and 240-2 serve as body pickup regions. Aperson skilled in the art will recognize there may be many alternatives,modifications and variations. For example, depending on differentapplications and design needs, the frame-like body pickup region 240-1and the frame-like source region 230S-1 may share a contact plug, andthe frame-like body pickup region 240-2 and the frame-like source region230S-2 may share a contact plug.

As mentioned above, a silicide structure (not shown) can be formed onthe drain regions 230D-1 and 230D-2, the frame-like source regions230S-1 and 230S-2, and the frame-like doped regions 240-1 and 240-2.

The high-voltage device 200 further includes a frame-like doped region242-1 disposed in the well region 210-1, and a frame-like doped region242-2 in the well region 210-2. The frame-like doped region 242-1 ispartially covered by the frame-like gate structure 220-1, partiallycovered by the frame-like source region 230S-1 and the frame-like dopedregion 240-1, and partially covered by the frame-like isolation 204-1;therefore, the frame-like doped region 242-1 may not be observed fromthe top view. Similarly, the frame-like doped region 242-2 is partiallycovered by the frame-like gate structure 220-2, partially covered by theframe-like source region 230S-2 and the frame-like doped region 240-2,and partially covered by the frame-like isolation 204-2; therefore, theframe-like doped region 242-2 may not be observed from the top view. Theframe-like doped regions 242-1 and 242-2 include the second conductivitytype. A doping concentration of the frame-like doped region 242-1 and adoping concentration of the frame-like doped region 242-2 are the same.Further, the doping concentrations of the frame-like doped regions 242-1and 242-2 are less than doping concentrations of the frame-like dopedregions 240-1 and 240-2, in some embodiments, the frame-like dopedregions 242-1 and 242-2 can be referred to as a high-voltage p-type body(HVPB). In some embodiments, a side edge of the frame-like doped region242-1 can be in contact with the well region 210-1, and a side edge ofthe frame-like doped region 242-2 can be in contact with the well region210-2.

The high-voltage device 200 further includes another frame-like dopedregion 244-1 under the frame-like doped region 242-1 and separated fromthe well region 210-1 by the frame-like well region 212-1, and aframe-like doped region 244-2 under the frame-like doped region 242-2and separated from the well region 210-2 by the frame-like well region212-2. The frame-like doped region 244-1 surrounds the frame-like gatestructure 220-1, and the frame-like doped region 244-2 surrounds theframe-like gate structure 220-2. The frame-like doped regions 244-1 and244-2 include the second conductivity type. A doping concentration ofthe frame-like doped region 244-1 and a doping concentration of theframe-like doped region 244-2 are the same. Further, the dopingconcentrations of the doped regions 242-1 and 242-2 are greater than thedoping concentrations of the doped regions 244-1 and 244-2. In someembodiments, a top surface of the frame-like doped region 244-1 is incontact with the frame-like doped region 242-1, and side edges and abottom surface of the frame-like doped region 244-1 are in contact withthe frame-like well region 212-1. Similarly, a top surface of theframe-like doped region 244-2 is in contact with the frame-like dopedregion 242-2, and side edges and a bottom surface of the frame-likedoped region 244-2 are in contact with the frame-like well region 212-2.

In some embodiments, the high-voltage device 200 includes anotherframe-like isolation 208 surrounding the isolations 204-1 and 204-2, thewell regions 210-1 and 210-2, the frame-like well regions 212-1, 212-2,214-1 and 214-2, the frame-like doped regions 240-1, 240-2, 242-1,242-2, 244-1 and 244-2, the frame-like source regions 230S-1 and 230S-2,the frame-like gate structures 220-1 and 220-2, and the drain regions230D-1 and 230D-2.

In some embodiments, a frame-like doped region 250 a is disposed betweenthe frame-like isolation 204-1 and the frame-like isolation 208.Further, a doped region 250 b is disposed between the frame-likeisolation 204-1 and the frame-like isolation 204-2. The frame-like dopedregion 250 a and the doped region 250 b are coupled. The high-voltagedevice 200 further includes a frame-like doped region 252 a and aframe-like well region 254 a under the frame-like doped region 250 a,and a doped region 252 b and a well region 254 b under the doped region250 b. The doped region 252 b is coupled to the frame-like doped region252 a, and the well region 254 b is coupled to the frame-like wellregion 254 a.

The frame-like doped region 250 a, the doped region 250 b, theframe-like doped region 252 a, the doped region 252 b, the frame-likewell region 254 a and the well region 254 b include the secondconductivity type. A doping concentration of the frame-like doped region250 a and a doping concentration of the doped region 250 b are the same,a doping concentration of the frame-like doped region 252 a and a dopingconcentration of the doped region 252 b are the same, and a dopingconcentration of the frame-like well region 254 a and a dopingconcentration of the well region 254 b are the same. Further, the dopingconcentrations of the frame-like doped region 250 a and the doped region250 b are greater than the doping concentrations of the frame-like dopedregion 252 a and the doped region 252 b, and the doping concentrationsof the frame-like doped region 252 a and the doped region 252 b aregreater than the doping concentrations of the frame-like well region 254a and the well region 254 b. In some embodiments, the frame-like dopedregion 252 a is disposed under the frame-like doped region 250 a suchthat a bottom surface of the frame-like doped region 250 a is in contactwith the frame-like doped region 252 a. The frame-like well region 254 ais formed under the frame-like doped region 252 a, such that a bottomsurface and side edges of the frame-like doped region 252 a are incontact with the frame-like well region 254 a. Similarly, the dopedregion 252 b is disposed under the doped region 250 b such that a bottomsurface of the doped region 250 b is in contact with the doped region252 b. The well region 254 b is formed under the doped region 252 b,such that a bottom surface and side edges of the doped region 252 b arein contact with the well region 254 b. In some embodiments, theframe-like well region 254 a and the frame-like well region 254 b are incontact with both of the well regions 210-1 and 210-2.

In some embodiments, the frame-like doped region 250 a and the dopedregion 250 b may serve as guard rings for the high-voltage device 200.The frame-like doped region 250 a and the doped region 250 b allow anelectrical bias to be applied to the substrate 202 through theframe-like doped region 252 a, the frame-like doped region 252 b, theframe-like well region 254 a and the frame-like well region 254 b. Itshould be understood that the formation of the frame-like doped region250 a and the frame-like doped region 250 b is optional.

Additionally, the high-voltage device 200 has a line symmetryconfiguration about a central axis CA, as shown in FIG. 3. In someembodiments, the central axis CA pass through the doped region 250 b.Accordingly, arrangements of elements to the left of the central axis CA(i.e., the drain region 230D-1, the doped region 232-1, the frame-likeisolation 204-1, the frame-like gate structure 220-1, the frame-likesource region 230S-1, the frame-like doped regions 240-1, 242-1, 244-1,the well region 210-1, and the frame-like well regions 212-1, 214-1) areidentical to arrangements of elements to the right of the central axisCA (i.e., the drain region 230D-2, the doped region 232-2, theframe-like isolation 204-2, the frame-like gate structure 220-2, theframe-like source region 230S-2, the frame-like doped regions 240-2,242-2, 244-2, the well region 210-2, and the frame-like well regions212-2, 214-2). In some embodiments, the drain regions 230D-1 and 230D-2are electrically connected to a same connecting structure, theframe-like gate structures 220-1 and 220-2 are electrically connected toa same connecting structure, and the frame-like source regions 230S-1and 230S-2 are electrically connected to a same connecting structure.

According to some embodiments of the high-voltage device 200, a distanced can be defined between the edge 212 e-1 of the well region 212-1 andthe edge 210 e-1 of the well region 210-1, and between an edge 212 e-2of the well region 212-2 and the edge 210E-2 of the well region 210-2,as shown in FIG. 4. In some embodiments, the distance d can be betweenapproximately 2 μm and approximately 3 μm. In some comparativeapproaches, when the distance d is less than 2 μm, current may punchthough the well regions 210-1, 210-2 and thus such device may fail. Inalternative comparative approaches, when the distance d is greater than3 μm, such device may need more area to accommodate the well region andthus cannot be shrunk. In contrast to the comparative approaches, ananti-punch capability of the high-voltage device 200 can be improved bygreater than approximately 300%.

Further, in the high-voltage device 200, the well region 210-1 under theframe-like gate structure 220-1 and the well region 210-2 under theframe-like gate structure 220-2 can be fully depleted when thehigh-voltage device 200 is in an off state. In other words, frame-likefully depleted regions A may be formed when the high-voltage device 200is in the off state. The frame-like fully-depleted region A helps toincrease the breakdown voltage. In some embodiments, the breakdownvoltage of the high-voltage device 200 can be improved by greater thanapproximately 27%.

Because a channel width is increased by the frame-like gate structures220-1 and 220-2, an on-resistance of the high-voltage device 200 can bereduced.

The present disclosure therefore provides a high-voltage device having aframe-like gate structure. The frame-like gate structure helps to reducecurrent from the drain region through the drift region. Accordingly,breakdown voltage and anti-punch capability of the high-voltage devicecan be increased. Further, because the frame-like gate helps to improvethe anti-punch capability, a width of the n-type doped layer can bereduced, such that on-resistance can be reduced. In other words, thehigh-voltage device including the frame-like gate structure has anincreased breakdown voltage, an improved anti-punch capability, andreduced on-resistance.

According to one embodiment of the present disclosure, a high-voltagedevice is provided. The high-voltage device includes a substrate, afirst well region disposed in the substrate, at least a first isolation,a frame-like gate structure over the first well region and covering aportion of the first isolation, a drain region in the first well regionand separated from the frame-like gate structure by the first isolation,and a source region separated from the drain region by the firstisolation and the frame-like gate structure. In some embodiments, thefirst well region, the drain region and the source region include afirst conductivity type, and the substrate includes a secondconductivity type. The first conductivity type and the secondconductivity type are complementary to each other.

According to one embodiment of the present disclosure, a high-voltagedevice is provided. The high-voltage device includes a substrate,including a frame-like isolation disposed in the substrate, a frame-likegate structure over the substrate and covering a portion of theframe-like isolation, a drain region in the substrate and enclosed bythe frame-like isolation, a source region in the substrate and adjacentto the frame-like gate structure on a side opposite to the drain region,a first doped region under the drain region and separated from thesubstrate, and a second doped region under the source region andseparated from the source region and the substrate. In some embodiments,the drain region, the source region and the first doped region include afirst conductivity type, and the substrate and the second doped regioninclude a second conductivity type complementary to the firstconductivity type.

According to one embodiment of the present disclosure, a high-voltagedevice is provided. The high-voltage device includes a first frame-likeisolation and a second frame-like isolation separated from each other, afirst frame-like gate structure covering a portion of the firstframe-like isolation and a second frame-like gate structure covering aportion of the second frame-like isolation, a first drain regionenclosed by the first frame-like isolation and a second drain regionenclosed by the second frame-like isolation, a first frame-like sourceregion surrounding the first frame-like gate structure and a secondframe-like source region surrounding the second frame-like gatestructure, a first doped region surrounding the first frame-like gatestructure and the second frame-like gate structure, and a second dopedregion between the first frame-like gate structure and the secondframe-like gate structure. The second doped region is coupled to thefirst doped region. In some embodiments, the first drain region, thesecond drain region, the first frame-like source region and the secondframe-like source region include a first conductivity type, and thesubstrate, the first doped region and the second doped region include asecond conductivity type. The first conductivity type and the secondconductivity type are complementary to each other.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A high-voltage device comprising: a substrate; afirst well region in the substrate; a second well region in the firstwell region; a third well region in the first well region and the secondwell region at least a first isolation in the first well region; aframe-like gate structure over the first well region and covering aportion of the first isolation; a drain region in the first well regionand separated from the frame-like gate structure by the first isolation;and a source region, wherein in a plan view, the source region isseparated from the drain region by the first isolation and theframe-like gate structure, wherein the first well region, the drainregion and the source region comprise a first conductivity type, thesubstrate, the second well region and the third well region comprise asecond conductivity type, and the first conductivity type and the secondconductivity type are complementary to each other.
 2. The high-voltagedevice of claim 1, further comprising: a first doped region in the firstwell region and separated from the frame-like gate structure by thefirst isolation; a second doped region adjacent to the source region;and a third doped region under the second doped region, wherein thefirst doped region comprises the first conductivity type, and the seconddoped region and the third doped region comprise the second conductivitytype.
 3. The high-voltage device of claim 1, wherein a side edge of thesecond well region is in contact with the first well region.
 4. Thehigh-voltage device of claim 2, further comprising a fourth doped regionunder the third doped region, wherein the fourth doped region comprisesthe second conductivity type, and the fourth doped region is separatedfrom the first well region by the second well region.
 5. Thehigh-voltage device of claim 4, wherein a doping concentration of thethird doped region is greater than a doping concentration of the fourthdoped region.
 6. The high-voltage device of claim 1, wherein a dopingconcentration of the third well region is greater than a dopingconcentration of the second well region.
 7. The high-voltage device ofclaim 1, further comprising a second isolation disposed in the substrateand separated from the frame-like gate structure and the firstisolation, wherein the source region is disposed between the frame-likegate structure and the second isolation.
 8. The high-voltage device ofclaim 7, further comprising: a fourth well region in the substrate; afifth doped region in the fourth well region; and a sixth doped regionover the fourth well region and the fifth doped region, wherein thefourth well region, the fifth doped region and the sixth doped regioncomprise the second conductivity type.
 9. The high-voltage device ofclaim 1, wherein the first isolation has a frame-like configuration. 10.The high-voltage device of claim 7, wherein the second isolation has aframe-like configuration.
 11. A high-voltage device comprising: asubstrate; a frame-like isolation; a frame-like gate structure over thesubstrate and covering a portion of the frame-like isolation; a firstwell region in the substrate; a second well region in the first wellregion, wherein the second well region has a frame-like configurationsurrounding the frame-like gate structure; a drain region in thesubstrate and enclosed by the frame-like isolation; a source region inthe substrate and adjacent to the frame-like gate structure on a sideopposite to the drain region; a first doped region under the drainregion; and a second doped region under the source region, wherein thedrain region, the source region, the first well region and the firstdoped region comprise a first conductivity type, and the substrate, thesecond well region and the second doped region comprise a secondconductivity type complementary to the first conductivity type.
 12. Thehigh-voltage device of claim 11, wherein a bottom surface of the firstdoped region is spaced apart from the substrate by the first wellregion, and the second doped region is separated from the first wellregion by the second well region.
 13. The high-voltage device of claim11, further comprising: a third doped region over the second well regionand comprising the second conductivity type, wherein a sidewall of thethird doped region is in contact with the first well region; and a thirdwell region comprising the second conductivity type, wherein a portionof the third well region is in the first well region and a portion ofthe third well region is in the second well region, and the second dopedregion is between the third doped region and the third well region. 14.The high-voltage device of claim 13, wherein the third doped region hasa frame-like configuration, and the third well region has a frame-likeconfiguration.
 15. The high-voltage device of claim 11, wherein thesecond well region has a frame-like configuration, the source region hasa frame-like configuration, and the second doped region has a frame-likeconfiguration.
 16. A high-voltage device comprising: a first wellregion; a second well region in the first well region, wherein a sideedge of the second well region is in contact with the first well region;a third well region in contact with the first well region and the secondwell region; at least a first frame-like isolation in the first wellregion; a frame-like gate structure over the first well region andcovering a portion of the frame-like first isolation; a drain region inthe first well region and separated from the frame-like gate structureby the first frame-like isolation; a frame-like source region, whereinin a plan view, the frame-like source region is separated from the drainregion by the first frame-like isolation and the frame-like gatestructure; a frame-like second isolation enclosing the second wellregion, the first frame-like isolation, the frame-like gate structure,the drain region and the frame-like source region, wherein the firstwell region, the drain region and the frame-like source region comprisea first conductivity type, the second well region and the third wellregion comprise a second conductivity type, and the first conductivitytype and the second conductivity type are complementary to each other.17. The high-voltage device of claim 16, wherein the frame-like secondisolation is separated from the frame-like gate structure and theframe-like first isolation.
 18. The high-voltage device of claim 16,further comprising: a first doped region under the drain region; aframe-like second doped region adjacent to the frame-like source region;a frame-like third doped region under the frame-like second dopedregion; and a frame-like fourth doped region under the frame-like thirddoped region, wherein the first doped region comprises the firstconductivity type, and frame-like the second doped region, theframe-like third doped region and the frame-like fourth doped regioncomprise the second conductivity type.
 19. The high-voltage device ofclaim 16, wherein the frame-like source region is disposed between theframe-like gate structure and the frame-like second isolation.
 20. Thehigh-voltage device of claim 16, further comprising: a fourth wellregion adjacent to the first well region; a frame-like fifth dopedregion in the fourth well region; and a frame-like sixth doped regionover the fourth well region and the fame-like fifth doped region,wherein the fourth well region, the frame-like fifth doped region andthe frame-like sixth doped region comprise the second conductivity type.